X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from imf16aec.mail.bellsouth.net ([205.152.59.64] verified) by logan.com (CommuniGate Pro SMTP 5.1.9) with ESMTP id 2093112 for flyrotary@lancaironline.net; Sat, 09 Jun 2007 07:56:29 -0400 Received-SPF: none receiver=logan.com; client-ip=205.152.59.64; envelope-from=rusty@radrotary.com Received: from ibm56aec.bellsouth.net ([65.6.194.9]) by imf16aec.mail.bellsouth.net with ESMTP id <20070609115550.BQV9726.imf16aec.mail.bellsouth.net@ibm56aec.bellsouth.net> for ; Sat, 9 Jun 2007 07:55:50 -0400 Received: from rd ([65.6.194.9]) by ibm56aec.bellsouth.net with ESMTP id <20070609115550.KPZK27162.ibm56aec.bellsouth.net@rd> for ; Sat, 9 Jun 2007 07:55:50 -0400 From: "Russell Duffy" To: "'Rotary motors in aircraft'" Subject: RE: [FlyRotary] Re: Single rotor video Date: Sat, 9 Jun 2007 06:55:51 -0500 Message-ID: <000001c7aa8d$207e5790$6e01a8c0@rd> MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0001_01C7AA63.37A84F90" X-Priority: 3 (Normal) X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook, Build 10.0.6822 Importance: Normal Thread-Index: AceqPUYmnx02nrkeQFuOuvMIaqwcYwATe41A In-Reply-To: X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.3028 This is a multi-part message in MIME format. ------=_NextPart_000_0001_01C7AA63.37A84F90 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable I think Lynn is correct. Even a few pounds at the radius of a normal starter ring gear (as a flywheel) should make a noticeable difference. Hi Cary, You'd think it would help, but I had this engine mounted on a Kolb = airframe about a year ago, with one of Tracy's redrives. At the time, I tried = adding weight to the flex plate, and it didn't make any noticeable difference. = It should help, but I'm afraid it will have to be more than a few lbs. =20 My guess is that the forward and backward tip motion is mostly due to = the positive/negative thrust as the blades transition from forward motion to slowed/stopped/reversed = by torque reversals. Adjusting the blades to near zero angle should confirm = it. I think it's clear that this wouldn't happen if there was no pitch in = the blades, so I don't have any plans to try that experiment. Another = thought occurred to me yesterday though. There may be some tip stall going on, which would complicate matters a bit. When I first set up the prop, I = just picked a number for pitch. What I picked was 15 degrees, which turns = out to be way too much. On my early revisions of the RV-3 engine, I had a 3 = blade 68" Warp prop, and 15 degrees was one of the higher pitches I ever = tried. The single rotor prop is a 3 blade 72" prop, so even larger. Clearly, = 15 degrees is a bad choice, and might explain why I seem to needs so much = fuel to run it :-) =20 I could swear that I change it from 15 to 10 degrees, but can't find a record of doing that. I also noted that it took quite a lot of throttle = to get 4000 rpm for the video tests, so I'm thinking I never did change it. Can't wait to try it with a more reasonable pitch. =20 Rusty (gotta go fly the Wauchula gyro now) ------=_NextPart_000_0001_01C7AA63.37A84F90 Content-Type: text/html; charset="us-ascii" Content-Transfer-Encoding: quoted-printable Message

I think Lynn is correct.
Even a few pounds at the = radius of a=20 normal starter ring gear (as a flywheel) should make a
noticeable=20 difference.

Hi = Cary,

You'd = think it would=20 help, but I had this engine mounted on a Kolb airframe about a year ago, = with=20 one of Tracy's redrives.  At the time, I tried adding weight to the = flex=20 plate, and it didn't make any noticeable difference.  It should = help, but=20 I'm afraid it will have to be more than a few lbs. 

My guess is that the forward and backward tip motion is mostly due to = the=20 positive/negative thrust
as the blades transition from forward motion = to=20 slowed/stopped/reversed by torque reversals. Adjusting the blades to = near zero=20 angle should confirm it.

I think it's clear that = this wouldn't=20 happen if there was no pitch in the blades, so I don't have any plans to = try=20 that experiment.  Another thought occurred to me yesterday=20 though.  There may be some tip stall going on, which would = complicate=20 matters a bit.  When I first set up the prop, I just picked a = number for=20 pitch.  What I picked was 15 degrees, which turns out to be way too = much.  On my early revisions of the RV-3 engine, I had a 3 blade = 68" Warp=20 prop, and 15 degrees was one of the higher pitches I ever tried.  = The=20 single rotor prop is a 3 blade 72" prop, so even larger.  Clearly, = 15=20 degrees is a bad choice, and might explain why I seem to needs so much = fuel to=20 run it :-)  

I could swear that I = change it from 15=20 to 10 degrees, but can't find a record of doing that.  I also noted = that it=20 took quite a lot of throttle to get 4000 rpm for the video tests, so I'm = thinking I never did change it.  Can't wait to try it with a more=20 reasonable pitch. 

Rusty (gotta go fly the = Wauchula gyro=20 now)

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